1. Field of the Invention
The present invention relates to evaporative coolers, and more particularly pertains to an evaporative cooler utilizing both direct and indirect processes in a single unit.
2. Description of the Prior Art
Evaporative cooling (or swamp cooling) has existed for many centuries. People experience evaporative cooling when they step out of a swimming pool on a breezy day. The use of evaporative cooling for structures is thought to have begun in ancient Egypt with the use of wetted rags hanging in door and window ways. Today the technology has developed to high efficiency media types which have life expectancies of up to 5 years. Traditional swamp coolers utilize aspen wood fiber or synthetic mesh pads sprayed or soaked with water to achieve temperature reduction through evaporative cooling as air is blown across the wetted pads. The high efficiency media pads achieve higher, and more consistent, performance, which results in lower temperatures. The reduction of air temperature is the result of energy transferred from the hot air to the water as it changes from a liquid to a gas upon evaporation. As air is blown over the media, the rate of evaporation is increased dramatically. Since the air to be cooled is in direct contact with the water, this process is called direct or "wet" evaporative cooling. Evaporative coolers are very inexpensive to operate when compared to traditional air conditioning, and use less energy, and are thus more environmentally friendly.
Indirect evaporative cooling systems utilize an air exchanger to separate the evaporating water from the air stream to be cooled. Since the evaporated water is not in contact with the air stream, the air is cooled with no moisture added. This process is known as "dry" evaporative cooling.
Two-stage evaporative cooling systems employ combined indirect (dry) and direct (wet) evaporative cooling processes, resulting in an air temperature which is lower than that achieved by either of the processes independently, while producing air with a moisture content lower than that of traditional direct (wet) evaporative cooling.
Evaporative cooling has many advantages over other air cooling technologies, including: lower energy consumption, avoiding potentially environmentally harmful refrigerants used in mechanical refrigeration, improved indoor air quality through the air washing nature of evaporative cooling, and low operational costs.
The use of evaporative coolers is generally well known, and many patents have issued to various particular devices and systems employing evaporative cooling processes. Examples of such prior art patents include U.S. Pat. Nos. 3,148,442, 4,002,040, 4,582,126, 4,781,248, 4,913,776, 5,800,595, 5,816,318, and 5,927,097. The entire disclosures of each of the foregoing patents are hereby incorporated herein by this reference thereto.